The important point here is that it has been definitivly determined that this is not from an infection or the drainage of other necrotic debris. Everyone that has had neck surgeries knows that for serval days after a surgery they will put in drains so that the excess body fluids have a pathway out of the area. These are finally removed when sufficient drainage has taken place. Fistulas are usually allowed to drain, and the wound area should be kept really clean. Irrigate it daily with saline, if it is messy tape some gauze over it. If it smells bad, or the discharge from it seems excessive to you, or it dosen't resove in a short period of time and begin to heal, get your doctor to reevaluate the situation. If you begin to run a temperature, tell him right away.